Mellow Ezlo
Spoony Bard
What kind of rivals? Rivals like in Pokemon, then no. Rivals like Groose and Ralph, then yes, I would like to see more of them.
Yes.
There should be a moment where Link actually faces his rival in a sword battle.
As for the idea of Dark Link not being the "dark twin"... I don't agree, because, as the name suggests, he's SUPPOSED to be the dark twin. If anything I see Dark Link being created by Ganon or some other villain specifically to fight Link by basing him on Link's fighting style.